Abstract: Doppler Ultrasound techniques have been used for many years to measure the flow rate of fluids. One of the challenges in using these techniques is to separate fluid flow signal from background noise. The present invention is directed to methods and apparatus for automatically distinguishing fluid flow signal from noise. It is found that noise in Doppler ultrasound techniques has characteristic of a white Gaussian spectral distribution and the mean noise can be characterized as a constant. The present invention involves measuring ultrasonic signals, generating sets of discrete spectral components from these signals, and statistically determining a maximum likelihood estimation from the spectral components. This estimation is used to calculate the fluid velocity.

Abstract: This invention relates to a focused synthetic array wherein a different signal from a crossed beam antenna is converted to a bipolar video signal and applied as the input to a synthetic array processor. In another embodiment of the invention there is a separate reduction of each beam output from a crossed beam antenna to bipolar video signals with a separate application of asymmetrical amplitude weights to the two bipolar video records and a subsequent subtraction in the course of synthetic array processing.

Abstract: In a system for reducing sidelobes in adaptive receiving array antennas, an auxiliary signal is radiated through an omnidirectional antenna collocated with the phase center of an adaptive array antenna. The auxiliary signal is so transmited as to form a probe or pilot beam with a notch in the main-beam direction by transmitting through both the omnidirectional and the array antenna simultaneously. The relative phases of both antennas are controlled to obtain near-zero radiation in the main-beam direction. Adaptive control loops receive returns from the probe beam and adjust the weights of the receiving array antenna. The receiving array weights are used to form a low sidelobe antenna pattern for reception of the main radar signal, which is transmitted with a directional pattern. Either time or frequency separation may be used to distinguish the probe beam from the main beam.